Styrene is a common raw material of rubbery copolymers, such as styrene-butadiene copolymers (SBR), styrene-isoprene copolymers, and styrene-isoprene-butadiene copolymers (SIBR). These rubbery copolymers are often used in vulcanizable rubber compositions suitable for different components of tires, e.g., the tread, the bead, the sidewall, etc. Styrene raw materials used on an industrial scale are typically derived from petroleum-based hydrocarbons. Styrene is typically produced via the alkylation of petroleum-derived benzene with petroleum-derived ethylene.
Petrochemical-based hydrocarbons are fossil fuels, which by their nature, do not contain any “modern” carbon. Modern carbon, as defined herein, refers to the standard set forth in ASTM D6866. Generally speaking, under this standard, modern carbon contains the same 14C activity level (including the post-1950 correction) as the original oxalic acid radiocarbon standard (SRM 4990b). 14C, also known as carbon-14 or radiocarbon, is a radioactive isotope of carbon that occurs naturally and is found in plants and animals at approximately the same concentration found in the atmosphere. Due to radioactive decay, fossil fuels lack any measurable 14C activity, and, therefore, do not contain any modern carbon. Newer organic materials, including the biobased materials disclosed herein, will display 14C activity, and therefore will contain modern carbon.